The results of an experimental investigation of Methanol, Ethanol, Methane, and Ammonia as primary fuels for a high speed direct injection diesel engine are described. The fuels were added to the intake air and ignited by injection of a small amount of pilot diesel fuel (30 percent on energy basis). All of the four fuels were found applicable with Methane as the most suitable and Ammonia as the least suitable. Experimental data are presented regarding engine power output, efficiency, smoke and gaseous emissions, and the different types of combustion observed during the experiments are discussed. /GMRL/